The police officer sons of two south Texas law enforcement chiefs who made fighting corruption the cornerstones of their careers have been taken into custody on suspicion of waylaying drug caches coming across the border from Mexico.

Federal agents investigating several border departments west and south of McAllen arrested Jonathan Treviño, the son of Lupe Treviño, sheriff of Hidalgo County, and Alexis Espinoza, the son of Rodolfo Espinoza, Hidalgo’s police chief, the McAllen Monitor is reporting.

Agents took another pair of officers they didn’t identify into federal custody, and at least three more arrest warrants were outstanding. Sources told the newspaper two Hidalgo County Sheriff’s narcotics deputies are among those named in the warrants.

Warrants and related documents had not been filed by late Wednesday in U.S. District Court in McAllen. Federal investigators declined to discuss the investigation with the newspaper.

The probe, however, centers on something called the Panama Unit, a joint drug task force made up of Hidalgo County and Mission officers. Treviño and Espinoza are members of the unit.

“It’s just going to get real, real nasty, real, real quick,” an anonymous local investigator told the paper.

Sources told the paper the combination of authority and the absence of supervision had a way of making the Law Enforcement Code of Ethics disappear, particularly for Treviño, who “has gone unsupervised since the get-go.”

“With all the problems he’s had,” the source said, “they should have kicked Jonathan out years ago.”

“Everybody knew that kid was dirty,” another investigator told the paper. “It was just a matter of making a case.

Voters in Hidalgo County in November gave Treviño’s father a landslide third-term victory. Since his election in 2004 Treviño has promised to get on top of corruption in the county and secure the border.